Integrated circuit (IC) packages are commonly gang fabricated in the form of an array as several plastic packages are fabricated on a leadframe array or substrate that incorporates a plurality of leadframe or substrate units. There are several advantages associated with gang fabrication, including decreased labor, time, cost for fabrication and efficiency of materials used in fabrication. After gang fabrication, the individual IC packages are singulated using a conventional wafer saw.
One particular process for fabricating a leadless plastic chip carrier IC package is disclosed in U.S. Pat. No. 6,229,200, the contents of which are incorporated herein by reference. During this process, an array of leadless plastic chip carriers are fabricated by mounting singulated semiconductor dice to respective die attach pads of the leadframe strip, followed by wire bonding from the semiconductor dice to respective contacts and encapsulating in a molding compound. The leadframe strip is then mounted to a wafer saw ring or presented on a precision truck table, and saw-singulated.
In other packages, such as chip scale packages (CSP), IC devices are arrayed in a pattern on the surface of a substrate and the packages are diced into single units using a saw blade.
It will be appreciated that accuracy and precise control during dicing or saw singulation is important to ensure package uniformity and reliability.
Conventional saw blades are generally circular, or disk-shaped and include a bore hole at the center of the saw blade for mounting the blade between a pair of flanges, on a spindle of a cutting machine. The saw blades are comprised of an abrasive material embedded in a softer matrix material and are generally referred to as diamond cutting wheels. Typically, the abrasive material is an industrial-grade diamond embedded in a metallic binder material.
With repeated dicing and saw singulation of molded array packages, the diamond cutting wheels wear and the sharp cutting edges of the wheels break down leading to a change in shape and contour of the cutting surfaces of the wheels. Break down of the cutting wheels causes increased loading of the wheels, imprecise and inaccurate singulation and dicing and increased heat generation during cutting, thereby imparting damage to the IC packages. Imprecise and inaccurate singulation results in IC packages with undesirable profiles and affects package body dimension and subsequent handling of the package. For example, precision pick and place tooling requires precise package profile and body dimension. Changes to the package profile and body dimension affect the accuracy and consistency of performance of the pick and place tooling.
In prior art fabrication processes, diamond cutting wheels are replaced when wheel wear is excessive in order to obviate IC package damage caused by wheel wear. The diamond cutting wheels, however, are relative costly and it is desirable to extend the life of the diamond cutting wheel to reduce cost.